Flashing signs having transistorized oscillator circuit



ET AL 3,427,590

Feb. 11,1969

F. L. HARNEY, JR FLASHING SIGNS HAV ING TRANSISTORIZED OSCILLATOR CIRCUIT Filed July 30. 1964 I NVENTORS HARNEY', JR. NORMAN F. HOARD FRANK L.

. ATTOR N EYS United States Patent 1 Claim ABSTRACT OF THE DISCLOSURE An illuminated sign designed to flash at a blink rate designed to capture the attention of the observer. This sign is battery operated and uses a transistorized circuit to intermittently energize a gaseous discharge lamp.

This invention relates generally to illuminated signs and more particularly relates to a battery operated, transistorized, portable, illuminated and flashing sign having a novel transistorized circuit and a unique gaseous discharge lamp.

The present invention is related to the field of illuminated safety and warning signs and in particular is directed toward a self-contained, portable, battery operated, transistorized, warning and control sign that economically transmits its safety message or warning continuously at a blink rate designed to capture the attention of the observer. The device as described herein is highly dependable, more economical and more practical than known in the prior art. The device further has an exceptionally long life, needs little maintenance and may be exposed to all types of weather conditions for extended periods without deleterious effects. These and other features of the present invention are achieved through the use of a unique, highly eflicient, cold cathode, all weather fluorescent-type gaseous illumination source or lamp in conjunction with a highly dependable transistorized circuit especially designed for the present application. The invention has further features in that the face thereof is designed to be readily interchangeable so that any type warning or control message may be displayed thereon. Other and further advantages of the present invention will be better understood when considered in conjunction with the following drawings in which:

FIG. 1 is a perspective view of one embodiment of the present invention; and

FIG. 2 is a schematic diagram of the electrical system including the illumination source used therein.

Referring now to FIG. 1, there is shown a perspective view of the sign which generally illustrates the external physical characteristics of the invention when it is used as a portable highway sign. All electrical and illuminating means are contained Within a sturdy rectangular housing 11 formed with an opening therein, which opening is covered with a transparent means displaying a legend thereon.

More specifically, housing 11 is seen to comprise a rectangular box of suitable size formed of sheet steel and having supporting means such as legs 12, 13, 14 and 15 attached thereto. The opening in case 11 is formed such that a transparent face plate 19 may be fixed over the opening in case 11. Since such a device may be exposed to all weather conditions, case 11 may be made Weatherproof by sealing of its seams and by the liberal use of weather stripping around the face plate 19. In order to service the interior components without disturbing face plate 19, case 11 may be provided with a rear access panel (not shown).

Referring once again to legs 12, 13, 14 and 15, it is seen that such legs may be attached to case 11 by any suitable means. One such means is shown as brackets 17 and 16 which are hollow cylindrical tubes closed at one end and secured such as by welding to each end of case 11.

For portability of the device 10 such legs should fit snugly into their respective brackets but be readily removable, and a handle 18 should be provided on the upper surface of case 11.

In place of legs 12, 13, 14, and 15 and their respective brackets, the case could be provided with another supporting means such as eyebolts provided in the upper surface so that it may be suspended by a chain or by bolting on a wall or other horizontal surface.

The face plate 19 consists of a transparent sheet covering the opening in case 11 and having a legend displayed thereon. Plate 19 consists of any readily available transparent material such as glass or plastic. Because of the likelihood of breakage when the device is used in exposed places, such as a highway, the plate should consist of a high impact plastic having a high coeflicient of light transfer with minimum deterioration under continuous exposure to the ultraviolet radiation emitted by the sun. One particular material found suitable is cellulose acetate butyrate formed in sheets .080 inch thick.

The message displayed on the face plate 19 may be of any particular shape, form, or color to best convey the desired information. The size of the letters used will, of course, depend upon the length of the message. The words, Caution, Danger, Accident, Slow, Detour, One-Way, Open Trench, Keep Right, etc. are only a few of the messages available to alert and warn the observer. Such messages may be produced in the face plate 19 by well known methods such as by vacuum forming. However other means may also be used since the length or form of the message may require them.

FIG. 2 discloses the specific details of the novel transistorized circuit and unique illuminating means used in the sign 10. The circuit is basically an oscillator designed to produce pulses capable of flashing lamp 20 on and off forty times per minute. This flash or blink rate has been found to best capture the attention of the observer. Such actuation of lamp 20 is accomplished by coupling the lamp 20 to an oscillator circuit through a tuned circuit and transformer 21 selected to provide a secondary voltage of about 7500 volts. A satisfactory tuned circuit comprises capacitor 22 and the secondary winding 23 of transformer 21.

The oscillator circuit now to be described consists of a voltage source 24 coupled to transistor 25 through the primary 26 of transformer 21 and a feedback circuit coupled to a voltage divider network and the base 37 of the transistor.

This oscillator operates in the following manner. When the transistor 25 is of the PNP type a positive voltage from source 24 is applied to emitter 35 through winding 26 and the base is normally biased slightly negative by means of a voltage divider network consisting of resistors 29, 30 and 31. This negative bias to base 35 permits a positive starting of the oscillator with a fast pulse rise time when capacitor 40 is maintained across source 24 to reduce its effective impedance. The duration of the series of oscillation pulses is determined by resistors 32 and 33 and capacitor 34 located between primary 26 and tertiary 27, for when the charges on capacitor 34 accumulate to the point where it exceeds the negative voltage appended to base 37, the transistor 25 shuts off. Once transistor 25 shuts off, the charges on capacitor 34 begin to bleed off through the voltage divider network to ground. When the charges on capacitor 34 fall below the negative bias applied to base 37 by the voltage divider network, the transistor turns on and charge once again begins to accumulate on capacitor 34 to repeat the cycle.

A number of improvements is also shown in this figure. For example, a double base Zener diode 28 is connected in parallel with winding 27 in order to stabilize the circuit by limiting the maximum feed back voltage applied to base 37. Resistor 32 is preferably a thermistor in order to stabilize the circuit over a temperature range of 20 F. to +130 F. and resistor 29 is voltage variable to compensate for decreasing voltage from source 24 caused by continued use. A variable resistor may be substituted for fixed resistor 30 to provide an easily adjustable flash or blink rate. The range of adjustment may be limited by the use of a fixed resistor in series with the variable resistor to restrict the flash or blink rate within usable range.

As previously mentioned, the above-described circuit is used in conjunction with the unique lamp 20. Lamp 20 is an elongated hollow cylindrical or tubular, gas filled, body, of a transparent dielectric such as glass, sealed at either end with electrodes and 36 and having a fluorescent coating deposited on its interior surfaces. The fluorescent coating used may be a phosphor of barium titanium phosphate preferably deposited on its interior surfaces by any convenient method such as the flotation lacquer filming process which provides a smooth uniform coating of the phosphor. The gas filling used in the lamp should be one of the noble inert gases such as xenon. In the preferred embodiment, the lamp 20 is made, for example, of a tubing 12 feet long having an inner diameter in the order of 12 to 15 mm., arranged in a grid fashion, filled with xenon at a pressure of about 50 microns and having iron electrodes 35 and 36 fitted to the ends thereof. This length, diameter and pressure provides an impedance of about 50,000 ohms for which the previously described circuit was designed. The described lamp 20 has a high efficiency of emitted visible light when high voltage pulses in the order of 7500 volts peak at a repetition rate of 1000 to 1500 pulses per second are applied to the electrodes 35 and 36. Because of the low gas pressure and physical size of the tube being used, ionization of the xenon gas occurs and the resultant electron beam is not constricted thus permitting direct electron bombardment of the fluorescent phosphor coating in addition to excitation of the coating by the emission spectrum of the gas itself. This direct electron bombardment of the phosphor without constriction of the beam as Well as excitation by the emission spectrum of the gas provides a high efficiency of emission of visible light during intermittent operation that has heretofore been unavailable. This tube is capable of operation over a temperature range of 20 F. to 130 F.

The described pressure in the tube may be varied within wide limits. For example, it has been found that the pressure may be varied from 20 to 100 microns. Since maximum visible light emission occurs at a pressure of 20 microns when the pulse repetition rate is in the order of 1200 pulses per second, this pressure is most desirable.

However, this optimum pressure is diflicult to maintain and in practical embodiments a pressure of 50 microns is used. It has further been found that satisfactory operation of the tube is obtained over a broad range of peak striking voltages of 5,000 to 10,000 volts and peak ionization current limited to 10 to 20 milliamperes. The circuit previously described meets these requirements and when it produces an intermittent train of unidirectional high voltage pulses approximately 30 microseconds Wide with the repetition rate in the order of 1200 pulses per second, the lamp flashes at the optimum rate of 40 flashes per minute which has been found to best capture the notice of the observer.

Other and further variations within the scope of this invention will occur to those versed in the art. It is accordingly desired that the appended claim be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. An electronic system comprising, a gas discharge lamp, a constant voltage source, a voltage divider network, a transistor having base, emitter and collector electrodes, a transformer having primary, secondary and tertiary windings, said primary winding in series with the voltage source and across the emitter and collector electrodes of said transistor and in parallel with the voltage divider network and a first capacitor, said voltage divider network comprising a thermistor and at least one resistance, a second capacitor in series with the secondary winding of the transformer and said lamp, a feedback loop to said base consisting of said tertiary winding in parallel with a double base Zener diode and a thermistor, resistor, capacitor combination and in series with a portion of said voltage divider network and said primary winding, said transistor being of the blocking type pulse oscillatory class using inductive feedback with its period determined by the time constant of the base resistor-capacitor combination whereby said discharge lamp is periodically excited as a series element of said secondary winding.

References Cited UNITED STATES PATENTS 2,596,509 5/1952 Ranby 252301.4 2,731,585 1/1956 Rosseau 315--248 2,930,989 3/1960 Krieger 3311 12 2,982,881 5/1961 Reich 331-412 3,175,098 3/1965 Grace 307-885 3,181,084 4/1965 Attwood 331112 X 2,223,425 12/1940 McKeag 313-109 X 2,406,146 8/1946 Holmes 3l3-220 X 3,016,478 1/1962 Kadell 3 l5206 ROBERT SEGAL, Primary Examiner.

PALMER C. DEMEO, Assistant Examiner.

U.S. C1. X.R. 

